This invention pertains generally to the field of optical electronic devices and particularly to optical devices of the type used in optical communication networks.
Optical fiber communication networks are being increasingly utilized for both voice and data communication. Wavelength division multiplexing (WDM) has become the method of choice for increasing the data-carrying capacity of fiber optic systems. With WDM, many (typically from 4 to 40) data streams are carried along a single fiber, using a separate wavelength for each. Redirecting the flow of information in conventional fiber optic systems requires that the optical data streams be separated, converted to electronic signals, and then routed electronically to the next span of fiber in the network. The conversions from light to electronics to light greatly limits the speed and flexibility of present fiber optic systems. To better utilize the full potential of such optical networks, efforts have been directed to the development of optical switching devices which do not require conversion of the optical signal to an electrical signal. The challenges presented for such optical switching devices are particularly significant in communication networks which utilize WDM. In certain WDM applications, it is necessary to route carriers at different wavelengths to different locations based on the wavelength of the carrier. In other applications, it may be desirable to transfer the signal from a carrier at one wavelength to a carrier at a different wavelength.
In accordance with the invention, switching of optical signals and wavelength interchange of optical signals in optical communication systems is carried out without requiring conversion of the optical signals to electrical signals, thereby allowing the capabilities of the optical switching networks to be more fully utilized and minimizing the cost of electronic components. The invention may be utilized for wavelength sensitive routers, wavelength interchange cross connects, wavelength add/drop multiplexers, spectral inverters for dispersion compensation, facilitation of wavelength hopping for data encryption, inter-conversions between wavelength division and time division multiplexing, and may be extended to three dimensions to permit logic, arithmetic, and wavelength-shifting operations to be carried out on two-dimensional optical arrays for image analysis or to implement free-space interconnects.
The invention utilizes a lattice body comprising sensitized regions arranged in a two-dimensional array in a matrix material, wherein the sensitized regions differ from the matrix material in the sign of the second order susceptibility. Preferably, the sensitized regions and matrix material have the same first order susceptibility. The lattice body may be formed of various semiconductor materials and ferroelectrics such as LiNbO3. Two optical signals at different carrier frequencies xcfx891 and xcfx892 are coupled into the lattice body to interact with the array. A pump signal having a frequency xcfx89p=xcfx891+xcfx892 is also coupled into the lattice body with the two optical signals. These signals may be collinear with one another or may intersect in the lattice body. The spacing and pattern of the sensitized regions in the array in the lattice body are selected to interact with the three optical signals so that an optical signal exits from the lattice body that is angularly displaced from the direction of propagation of the input optical signals and that comprises an optical signal at a carrier frequency xcfx892 that carries the information on the input signal at the carrier frequency xcfx891. Another optical signal exits from the lattice body angularly displaced from the direction of propagation of the input optical signals that comprises an optical signal at a carrier frequency of xcfx891 that carries the information on the input signal at the carrier frequency xcfx892. These two angularly displaced signals may then be received and separated from each other, as well as from the input signals at the carrier frequencies xcfx891, xcfx892 and xcfx89p and cap which pass through the lattice body and exit without deflection from the initial input direction of propagation. When the pump signal is not applied to the lattice body, no wavelength interchange occurs, and the input signals at the frequencies xcfx891 and xcfx892 exit from the lattice body without change in the direction of propagation. Thus, by switching the pump signal on and off, the wavelength interchanged angularly diverging signals can be switched on and off.
Further, by utilizing a pump light signal intensity that has a larger magnitude than that of the input optical signals, the wavelength interchanged outputs can have a greater optical intensity than that of the input signals, thus effectively providing signal amplification.
The lattice body can comprise sensitized regions formed, for example, in ferroelectrics by periodic poling of the ferroelectric material, or in semiconductors by selective disordering, to provide an opposite sign of the second order susceptibility in the sensitized regions from that of the matrix material. Lateral waveguides may be formed on the lateral sides of the lattice body to receive and guide light that has been deflected from the longitudinal direction of the incoming light by interaction with the lattice.
Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.